Ballast reactor transformer



O 1949- MAUERER 2,486,307

BALLAST REACTOR TRANSFORMER Original Filed Aug. 28, 1942 J7ZU67ZZ07.Zeapqld Mazzerez" Patented Oct. 25, 1949 BALLAST REACTOR TRANSFORMERLeopold Mauerer, Chicago, Ill., assignor to J efferson Electric Company,Bellwood, 111., a corporation of Illinois Continuation of applicationSerial No. 456,521, August 28, 1942. This application June 27, 1947,

Serial No. 757,568

3 Claims.

My invention relates to fluorescent lamp ballasts and more particularlyto high reactance auto transformers which are utilized as ballasts influorescent lamp circuits.

This application is a continuation of my application Serial No. 456,521,filed August 28, 1942, and now abandoned.

For the proper operation of fluorescent lamps from alternating currentsources, it is necessary to use a suitable reactor, and where the powersupply voltage is not the same as required for firing such lamps, anauto transformer is usually used to supply this voltage in connectionwith this reactor. Such a combination is often simplified by building anauto transformer which has the necessary leakage reactance. Since suchtransformers generally have been incorporated in the lighting fixture orare arranged to be attached to such a lighting fixture which isrelatively long and narrow, the transformer is limited by physicaldimensions which make the design of such transformers somewhat differentthan other transformer structures. When fluorescent lamps were firstintroduced, the ballast transformer arrangements were such that arelatively high starting current was permitted. Subsequent developments,however, have shown the need and desirability for reducing this startingcurrent. High reactance auto transformer ballasts of the long narrowtype were satisfactory in the conventional construction when the highstarting current was permissible, since the reactance characteristic wasone in which the reactance would drop to a very great extent from normaloperating current to short circuit current due to saturation of the casewhich provided a considerable amount of the total leakage path. It was,however, necessary to closely couple part of the secondary winding tothe primary winding because without this expedient the leakage would beso great as to not permit sufficient power output to the lamp. In orderto obtain both a lower starting current and sufficient power output, itis proposed in accordance with the present invention to provide aleakage path which does not saturate readily.

It is, therefore, an object of my invention to provide a high reactancetransformer for fluorescent lamps which will have a suitable reactanceso as to limit the starting current to a relatively low value.

Another object of my invention is to provide a high reactancetransformer for fluorescent lamps which will have a limited low valuestarting current and yet supply sufficient power output for runningoperation.

Still another object of my invention is to provide a high reactance autotransformer arrangement for use in fluorescent lamp circuits which isarranged so as to reduce the high flux density heretofore found in thesurrounding transformer case.

Other and further objects of my invention will be more readilyunderstood by reference to the following description taken in connectionwith the accompanying drawing wherein Fig. 1 is a cross section througha transformer made in accordance with a preferred embodiment of myinvention;

Fig. 2 is a circuit diagram of the transformer shown in Fig. l; and

Fig. 3 is a circuit diagram of a transformer similar to that shown inFigs. 1 and 2, but showing the use of magnetic shunts in addition to theleakage effect provided by the casing.

Referring more particularly to the figures, it will be remembered thatthe physical dimensions of ballast reactor transformers used inconjunction with fluorescent lamps require a relatively long narrow corestructure 5 to fit within the lamp fixture or transformer case. Inaccordance with my invention the primary winding may be composed of twoequal primary coils 6 and l disposed at opposite ends of a secondarycoil 8 as shown in Fig. 3. v The primary coils 6 and l are physicallyseparated from the secondary coil 8 by magnetic shunts 9 and II. Thecore 5 together with the coils 6, l, 8, and the magnetic shunts 9 and Hare mounted in a case of fluorescent lamp fixture. The primary coils l3and 'l are connected in series to form a primary winding and this hasbeen indicated by the legend input in the drawing. The secr ondary coil3 is connected in series with the primary coil 6 and l to form asecondary winding indicated in the drawing by the legend output, andhence it will be seen that this transformer arrangement is of the autotransformer type. The magnetic shunts 9 and H between the primary andsecondary coils restore the leakage lost by utilizing such coilarrangement and the resulting leakage path provides a more uniform fluxpath through out the current range of operation, thus producing a lowerstarting current. Such an arrangement therefore obviates the undesirableeffects encountered in previous conventional construction where theprincipal leakage fiux is concentrated through one portion of the casewhich soon saturates, thus permitting relatively high short circuit orstarting current values.

Referring more particularly to Figs. 1 and 2 of the drawing, there isillustrated an embodiment of my invention which also obviates theconditions arising heretofore by the leakage flux readily saturating thesurrounding case. In this embodiment a magnetic core I2 is provided withtwo primary coils I3 and I4 which are equal or unequal in number ofturns, dependent upon the a particular conditions encountered, and witha secondary coil I 5. The primary coils l3 and I4 are positionedadjacent the ends of the secondary coil I5 preferably so that theprimary coils are spaced from the secondary coil. Because of theproximity of the case I6 to the coils, it will be readily seen that twoleakage paths are provided between the primary coils and the secondarycoil, thus distributing the leakage flux sufliciently to reduce thepossibility of saturation of the case. Since in this arrangement a caseprovides a substantial part of the path for the leakage flux, it may bedesirable to use a special alloy steel for the case or to laminate thecase structure. The primary coils I3 and I4 are connected in series toform a primary winding. The secondary coil I5 is connected in serieswith the primary coils to form a secondary winding, and hence thisarrangement also is of the auto transformer type.

Therefore, in accordance with the present invention, there has beenprovided a transformer arrangement of the auto transformer type whichsupplies a relatively low starting current, yet supplies suificientpower to the lamp.

While, for the purpose of illustrating and describing my invention,certain specific embodiments have been shown, it, of course, will beappreciated that modifications may be made therein without departingfrom the spirit and scope of my invention as set forth in the appendedclaims.

I claim:

1. A ballast reactor transformer comprising a relatively narrowelongated case. formed of magnetic material and supporting therein acore structure, a secondary coil and two primary coils. said primarycoils being spaced from the ends of said secondary coil and all of saidcoils being spaced closely adjacent a wall of said case, there by toprovide a plurality of parallel leakage paths through said case, saidprimary coils being connected in series to form a primary winding, andsaid secondary coil being connected in series with said primary coils toform a secondary winding.

2. A transformer for fluorescent lamps comprising a relatively narrow,elongated case formed of magnetic material and having therein a corestructure, a secondary coil, a primary coil having a certain number ofturns, a second primary coil having a diiferent number of turns, saidsecondary coil being supported in spaced relation between said primarycoils, said case having a portion spaced closely adjacent said coils andforming substantial and parallel leakage paths between said coils, saidprimary coils being connected to form a primary winding, and saidsecondary coil being connected in series with said primary winding toform a secondary winding.

3. A high reactance transformer for fluorescent lamps comprising anarrow elongated case formed of magnetic material and having therein acore structure supporting thereon a secondary coil at the center and apair of primary coils separated from said secondary coil by magneticshunt core portions to provide parallel flux leakage paths of lowreluctance, said case being in close proximity to said coils therebyaugmenting the eiTect of said magnetic shunt portions of said core, saidprimary coils being connected in series to form a primary winding, andsaid secondary coil being connected in series with both said primarycoils to form a secondary winding.

LEOPOLD MAUERER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,954,557 Comstock N Apr. 10,1934 2,095,294 Sola Oct. 12, 1937 2,183,355 Mauerer Dec. 12, 19392,391,873 Boucher Jan. 1, 1946

